Linux Filesystem Hierarchy

Familiarising yourself with the Linux filesystem hierarchy is very useful, especially if you’re working in DevOps, system administration roles. It helps you:

• Troubleshoot system issues

• Understand logs and services

• Write correct paths in scripts/configs

• Debug package installations, system performance, etc.

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Overview of Important Linux Directories

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Simple short-forms to help retain:

• /etc = “etcetera” → miscellaneous configs

• /var = “variable” → data that changes often

• /usr = “unix system resources” (historically, not just userland)

• /dev = “devices”

• /proc = “processes” (runtime virtual info)

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What about /var and /lib? and /var/lib?

/var, /lib, and /var/lib are critical parts of the Linux filesystem, and it's very helpful to know how they relate and differ.

1. /var

   • As the name suggest /var stores variable (changing) data or the things that grow or change during system operation

   • This is opposite of /usr, which is static and read-only post-install

2. /lib

   • stores essential shared libraries needed by binaries in /bin and /sbin , you can think of it as a place to hold core system libraries.

   • Without /lib, the system can’t even boot properly

3. /var/lib

   • While /lib stores shared libraries and system libraries, /var/lib stores stateful runtime data for system services and apps

   • This is where where services track what they're doing

   • eg: /var/lib/docker is where docker service stores all it’s runtime variable data like volume, images and even overlays.

It is useful to understand this diff especially for DevOps engineers while working with services like docker!!

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While it is useful to familiarise with these commands, I do not think memorising them would stick with you as you often tend to forget things that you don’t use, so instead I recommend bookmarking this article for reference while actively poking around an actual systems, exploring these directories as you work on day to day tasks and this will help you stick with it in the long run as you are figuring out details about each directory as your requirements instead of directly asking chat-gpt to find it for you.

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